Today, digital image acquisition has two approaches. The first, based on charge coupled device (CCD) sensors, dominates the consumer market. The second approach is based on CMOS photoreceptor sensors.
The process used to fabricate CCD sensors limits their integration with clock drivers, A/D converters, or image processing circuits. As a result, multiple chips are required to complete systems that use CCD sensors.
On the other hand, the CMOS sensor technology enables integrated circuits to be built that contain the sensor array as well as circuitry for analog-to-digital conversion, image processing, and other still and video image processing.
Often, digitized images are compressed in order to store the data or to transmit the data over a telecommunications channel. There is a considerable amount of redundancy in a typical image, and often lossy compression, which suppresses some of the less noticeable components of the image, is used. In a typical image acquisition system, a CCD camera is followed by an A/D converter and then an expensive compression chip compresses the data. Compression may also be necessary to meet bandwidth requirements of a computer system.